Segment Reporting - Schedule of Current Reportable Segments by Segment Profit (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Segment Profit		$ 142		$ 284
Share-based compensation		42		75
Transaction and integration expenses	[1]	3		9
Restructuring		14		20
Other	[2]	8		11
Depreciation		18		35
Intangible amortization expense		80		159
Operating (Loss) Income		(23)		(25)
Gain from change in fair value of financial instruments		(50)		(63)
Gain from change in fair value of tax receivable agreement		(38)		(43)
Interest expense		29		58
Other (income) expense, net		(7)		(8)
Income (Loss) Before Income Tax Benefit		43		31
Alight Holdings
Segment Reporting Information [Line Items]
Segment Profit			$ 145		$ 278
Share-based compensation			3		5
Non-recurring professional expenses	[3]		9		18
Restructuring			2		9
Other	[2]				(5)
Depreciation			25		49
Intangible amortization expense			50		100
Operating (Loss) Income			56		102
Interest expense			61		123
Other (income) expense, net			1		9
Income (Loss) Before Income Tax Benefit			(6)		(30)
Employer Solutions
Segment Reporting Information [Line Items]
Segment Profit		147		289
Employer Solutions | Alight Holdings
Segment Reporting Information [Line Items]
Segment Profit			138		274
Professional Services
Segment Reporting Information [Line Items]
Segment Profit		(3)		(3)
Professional Services | Alight Holdings
Segment Reporting Information [Line Items]
Segment Profit			$ 7		7
Hosted Business
Segment Reporting Information [Line Items]
Segment Profit		$ (2)		$ (2)
Hosted Business | Alight Holdings
Segment Reporting Information [Line Items]
Segment Profit					$ (3)

[1] Transaction and integration expenses includes activity related to acquisitions.

[2] For the three and six months ended June 30, 2022, Other primarily includes expenses related to debt refinancing completed in the first quarter of 2022 and other non-operational expenses, offset by Other income, net. For the three and six months ended June 30, 2021, Other includes long-term incentive expenses, offset by Other expense, net.

[3] Non-recurring professional expenses includes external advisor and legal costs related to the Company’s Business Combination completed in 2021.